On the mechanism of dehalogenation of methyl halides (Br and Cl) on Ag(111) and Au(111) surfaces: A DFT study

The dehalogenation reaction mechanism of CH₃X (X = Br, Cl) on Ag(111) and Au(111) surfaces is explored computationally. It is found that the CH₃X species are stronger adsorbed on Au(111) surface than on Ag(111) surface due to the increased charge transfer between the adsorbent and the surface. The dehalogenation on Au(111) and Ag(111) surface is slow due to large activation energy barriers. In presence of water, the release of CH₄ is plausible. CH₄ is also released when pre-adsorbed ^⁎H atoms are on the Ag(111) and Au(111) surfaces. The calculations indicate that the presence of co-adsorbents, mainly charged co-adsorbates, affects the reaction kinetics of CH₃X dehalogenation as their adsorption is accompanied by charge transfer, thus altering the electronic charge of the surface. It is proposed that the kinetics of the dehalogenation of CH₃X depends considerably on the charge on the metallic surface. Ag(111) is found to be a more promising catalyst for the dehalogenation of CH₃X than Au(111).